Compression and deaeration of powders

ABSTRACT

Powders are compressed and deaerated between vacuum cylinders which are arranged in groups requiring different vacuum and connected to a common vacuum line. Valve control means in said line automatically and continuously adjusts the vacuum pressure for the groups of cylinders.

United States Patent [72] Inventor Friedrich Loffler [50] Field of Search 18/2 HA, 9, Bruhl, Germany 10, DIG. 60, 12 DR, 29, 1 1, DIG. 62; 264/101, [2]] Appl. No. 55,398 102; 162/368, 364, 252; 25/21, 26, 76 [22] Filed July 16, 1970 45 1 Patented Jan. 4, 1972 1 References Cited [73] Assignee Deutsche Gold-Und Silber-Scheideanstalt UNITED STATES PATENTS Vomwls 1,990,434 2/1935 Kohler 264/101 x Frankfurt Germany 2,149,790 3/1939 R06SCh..... 18/DIG. 60 21 Pnomy May 12, 1967 2,855,829 10/1958 Allemann.... 162/364 x Germany 3,335,462 8/1967 Grigull et al. 264/102 X D 53061 3,440,138 4/1969 Smith 162/364 x Continuation-ln-part of appllcatlon Ser. No. 724,566, Apr. 26, 1968, now abandoned. Prlmwy EmmmerfiRobert p r, Jr. This application July 16, 1970, s Att0rneysFranc1s D. Stephens and Hugo Huemg, Jr. 55,398

ABSTRACT: Powders are compressed and deaerated between [54] COMPRESSION AND DEAERATION 0 POWDERS vacuum cylinders which are arranged in groups requiring dif- 2 Chims 1 Drawing ferent vacuum and connected to a common vacuum line.

Valve control means in said line automatically and continu- [52] Cl 3 0 ously adjusts the vacuum pressure for the groups of cylinders. [51] Int. Cl ..B29e 15/00, B291- 5/02 VA CUUM PUMP mm mm 35321247 INVENTOR Friedrich Ldffler P VACUUM PUMP COMPRESSION AND DEAERATION F POWDERS This is a continuationinpart of my application Ser. No.

724,566, filed Apr. 26, 1968, now abandoned. An apparatus and method for increasing the volumetric weight of a powder of pulverluent material with the use of vacuum, or subatmospheric pressure together with mechanical pressure is known in connection with a single machine. The pulverluent material is compressed between a pair of rotating evacuated cylinders having gaspermeable filter surfaces as, for example, perforated hollow cylinders. The air contained in the powder by reason of a previous grinding is drawn out of the mass of material by the vacuum in the two cylinders and the powder is then mechanically pressed in the space between the rotating cylinders. in this space, the actual compression is done mechanically under the vacuum.

For finely powdered materials, such as soot, silicic acid or silicates, which are used as fillers in the rubber industry or for other purposes, it is often the case that the ability of the powders to disperse in elastomers and polymers depends upon the degree of compression. With the increase in the volumetric weight, the materials must maintain the characteristic that the fineness of the powder particles is neither lost nor impaired. However, in practice, it has been found that by applying pressure to obtain maximum compression of silicic acid and silicates, nodules or lumps are formed which cannot be satisfactorily or easily dispersed in soft types of rubber. The formation of lumps in the very fine material lessens only when the speed of the cylinders is increased while the distance between the cylinders is unchanged. The speed of the cylinder will be different, dependent upon the type of material being compressed. Although this makes it possible to reduce the danger of forming lumps, however, the amount of compression resulting from this known procedure is also reduced and the volume which the powder occupies becomes larger, which is undesirable.

The formation of lumps will lessen also when the distance between the cylinders is increased and if at the same time the speed of the rotating cylinders is lessened to retain the same degree of compression.

However, even with using the latter technique, there is an undesirable increase in the volume of the processed powder and the technique is clumsy.

The object of this invention is to produce an apparatus which can be adjusted to control the vacuum in the cylinders to obtain any desired degree of deaeration of the powder so that the compressed powder is either heavily or lightly deaerated without being lumpy. The vacuum in the cylinders of a single machine can be manually controlled by use of a valve which can be opened or closed according to the corresponding vacuum required which can be read on the manometer. However, such manual operation is not feasible where several compression units connected to a common vacuum line are to be operated at the same time. In such case, manual control is must too clumsy, too expensive and also too inaccurate because of the various pressures occurring in the plurality of cylinders.

In this invention, the vacuum in the deaerating cylinders is made automatically adjustable. This is accomplished, for example, by means of controller sensing the subatmospheric pressure in a vacuum line to operate a pneumatic pressure control valve which acts continuously so that the controller for the valve and the valve form an operative unit. The desired vacuum, which must be less than the vacuum pulled by the pump, can be gradually manually adjusted, by means of a knob, to alter the setting of the pressure controller. The apparatus is operated so that when the vacuum becomes too high the line is throttled, and vice versa.

The advantage of using this automatically adjustable vacuum control in place of a solely manual operation is in that, when a plurality of compression units are connected to a single vacuum source, it is possible to easily and accurately adjust the entire system to any desired degree of deaeration. In practice, this means that a plant which must produce heavily deaerated as well as lightly deaerated powdered material at the same time can save costs, while, on the other hand, it 18 possible to obtain the desired uniform compression of each of the powdered materials for the further precessing of the powders as a filler in elastomers and polymers with good dispersion ability.

The means by which the objects of the invention are obtained are described more fully with reference to the accompanying schematic drawing which shows groups of deaerating and compression units connected to a common vacuum line.

The system shown is composed of two groups of deaerating and compressing units. Any number of such groups may be provided. it is assumed that group 1 operates on vacuum line 3 at a vacuum of 8,000 mm. WS Vac and group 2 operates on vacuum line 3a at a vacuum of 3,000 to 6,000 mm. WS Vac. Each unit has a pair of rotatable cylinders 1a and 1b between which the powder flows. The cylinders are hollow and have gas permeable filter surfaces.

These cylinders are connected to a common vacuum line 3, 3a joined to a vacuum pump P. A control valve 4 is inserted between lines 3 and 3a, between groups 1 and 2. A controller 5 is connected to the vacuum'line 3a serving group 2 through line 6 to automatically and continuously sense the subatmospheric pressure in line 3a and being connected to valve 4 to maintain a given pressure in group 2. Control 5 is shown also as being gradually adjustable by manually operated knob 7, so that the setting for operation of the machines in group 2 may be altered.

Having now described the means by which the objects of this invention are obtained,

I claim:

1. An apparatus for compressing and deaerating pulverluent materials comprising a plurality of compressing machines each machine having a pair of gaspermeable filtersurfaced rollers between which the materials are compressed, a vacuum pump to develop a high vacuum, a first vacuum line connecting each machine of a first group of said compressing machines to said vacuum pump, a second group of machines each requiring a lesser vacuum, a second vacuum line connecting each machine of said second group of machines, an adjustable valve connecting said second vacuum line to said first vacuum line, and automatic pressure sensing and valve adjusting means operatively connected to said second vacuum line and to said adjustable valve, whereby the vacuum in said second vacuum line may be adjusted to give a desired vacuum to all of said second group of machines, and the vacuum to said second group of machines will not vary as the vacuum pump is adjusted to give a desired vacuum to said first group of machines.

2. The apparatus of claim 1 including further manually operative means to adjust the setting of said sensing means to change the vacuum maintained in said second vacuum line. 

1. An apparatus for compressing and deaerating pulverluent materials comprising a plurality of compressing machines each machine having a pair of gas-permeable filter-surfaced rollers between which the materials are compressed, a vacuum pump to develop a high vacuum, a first vacuum line connecting each machine of a first group of said compressing machines to said vacuum pump, a second group of machines each requiring a lesser vacuum, a second vacuum line connecting each machine of said second group of machines, an adjustable valve connecting said second vacuum line to said first vacuum line, and automatic pressure sensing and valve adjusting means operatively connected to said second vacuum line and to said adjustable valve, whereby the vacuum in said second vacuum line may be adjusted to give a desired vacuum to all of said second group of machines, and the vacuum to said second group of machines will not vary as the vacuum pump is adjusted to give a desired vacuum to said first group of machines.
 2. The apparatus of claim 1 including further manually operative means to adjust the setting of said sensing means to change the vacuum maintained in said second vacuum line. 